Thermal stereolithography

ABSTRACT

Apparatus for and related methods of forming three-dimensional objects out of a building material, which is normally solid, but which is flowable when heated. In one embodiment, a support material is used to fill in portions of layers which are not to be solidified as part of the object, thus providing support to otherwise unsupported portions of other layers. Advantageously, the support material is also normally solid and flowable when heated, and has a lower melting point than the building material enabling the support material to later be removed without damaging the object. In an alternative embodiment this support material can be used to build a support such as a web support, or the like, for supporting an object surface from a second surface. In another alternative embodiment, such an apparatus is combined with a conventional stereolithographic apparatus to provide means for forming an object out of conventional stereolithographic materials, but utilizing a normally solid but thermally-flowable support material to provide support to the object, either on a layer-by layer basis, or by building supports such as web supports.

This application is a continuation of co-pending U.S. patent applicationSer. No. 08/148,544 filed Nov. 8, 1993, allowed, now Pat. No. 5,501,824which is a continuation of U.S. patent application Ser. No. 07/900,001filed Jun. 17, 1992, now abandoned; which is a continuation of U.S.patent application Ser. No. 07/592,559 filed on Oct. 4, 1990, now U.S.Pat. No. 5,141,680. U.S. Patent Application Ser. No. 182,801, filed Apr.18, 1988.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to the stepwise layer by layerformation of a three-dimensional object through application of theprinciples of stereolithography, and more specifically, to the formationof such an object utilizing materials which are normally solid, butwhich are made flowable upon the application of thermal radiation.

II. Background of the Invention

Several model building techniques have recently become available forbuilding three-dimensional objects in layers. One such technique isstereolithography, which is described in U.S. Pat. Nos. 4,575,330 and4,929,402 (hereinafter the '330 and the '402 patents), the disclosuresof which are hereby fully incorporated by reference herein as though setforth in full. According to the principles of stereolithography, athree-dimensional object is formed layer by layer in a stepwise fashionout of a material capable of physical transformation upon exposure tosynergistic stimulation. In one embodiment of stereolithography, layersof untransformed material such as liquid photopolymer or the like aresuccessively formed at the working surface of a volume of the liquidphotopolymer contained in a container. The untransformed layers aresuccessively formed over previously-transformed material. The process offorming these untransformed layers is known as a recoating step, and isdescribed in detail in U.S. Pat. No. 5,174,931.

Upon formation, the untransformed layers are selectively exposed tosynergistic stimulation such as UV radiation, or the like, whereuponthey form object layers. Moreover, upon transformation into the objectlayers, the untransformed layers typically adhere to thepreviously-formed layers through the natural adhesive properties of thephotopolymer upon solidification. Additional details aboutstereolithography are available in the following U.S. patents andco-pending patent applications, all of which, including appendices, arehereby fully incorporated by reference herein as though set forth infull:

    ______________________________________                                        Ser. No.  Date       Inventor(s) Status                                       ______________________________________                                        U.S. 182,830                                                                            4/18/88    Hull et al. U.S. Pat. No.                                                                 5,059,359                                    U.S. 183,016                                                                            4/18/88    Modrek      U.S. Pat. No.                                                                 4,996,010                                    U.S. 182,801                                                                            4/18/88    Hull et al. U.S. Pat. No.                                                                 4,999,143                                    U.S. 183,015                                                                            4/18/88    Smalley     U.S. Pat. No.                                                                 5,015,424                                    U.S. 268,429                                                                            11/8/88    Modrek et al.                                                                             U.S. Pat. No.                                                                 5,076,974                                    U.S. 268,837                                                                            11/8/88    Spence et al.                                                                             U.S. Pat. No.                                                                 5,123,734                                    U.S. 268,816                                                                            11/8/88    Spence      U.S. Pat. No.                                                                 5,058,988                                    U.S. 268,907                                                                            11/8/88    Spence et al.                                                                             U.S. Pat. No.                                                                 5,059,021                                    U.S. 331,644                                                                            3/31/89    Hull et al. U.S. Pat. No.                                                                 5,184,307                                    U.S. 339,246                                                                             4/7/89    Hull et al. U.S. Pat. No.                                                                 5,140,592                                    U.S. 429,435                                                                            10/30/89   Smalley et al                                                                             U.S. Pat. No.                                                                 5,130,064                                    U.S. 365,444                                                                            6/12/89    Leyden et al.                                                                             U.S. Pat. No.                                                                 5,143,663                                    U.S. 427,885                                                                            10/27/89   Spence et al.                                                                             U.S. Pat. No.                                                                 5,133,987                                    U.S. 429,911                                                                            10/27/89   Spence et al.                                                                             U.S. Pat. No.                                                                 5,182,056                                    ______________________________________                                    

In conventional embodiments of a stereolithographic apparatus, thematerial used is normally flowable so that it can be disposed onto aworking surface in preparation for exposure to the synergisticstimulation. Conventional materials which are typically used arephotopolymers which solidify upon exposure to UV radiation from a UVlaser or the like.

The use of these conventional materials is sometimes problematic, sincethey can be toxic when placed in contact with the skin, and are alsodifficult to dispose of easily. The use of UV radiation from UV lasersis also sometimes problematic because of the potential injury to thehuman eye. As a result, the use of this radiation must be controlled,and precautions taken, to minimize the risk of eye injury. Moreover, thetime required for the photopolymers to solidify upon exposure to the UVradiation can be prohibitively long. Finally, these materials aretypically very viscous, so that the time required to form a fresh layerof material over the working surface in anticipation of the formation ofthe next object cross-section can be prohibitively long.

Another problem with conventional stereolithographic apparatus is thedifficulty of rapidly substituting materials throughout thepart-building process, which would enable different portions of the samepart to be formed out of different materials having different propertiessuch as color, conductivity, and the like. Rapid material substitutionis difficult in a conventional stereolithography apparatus, since thematerial used to build the part is typically contained in a container,and it is difficult or time-consuming to be able to substitute differentcontainers throughout part building.

Rapid material substitution, however, would be beneficial. When buildingpart supports, such as web supports described in U.S. Pat. No.4,999,143, for example, the ability to use a different material for thesupports compared with the part would be desirable, because the supportscould then be constructed out of a material which could more easily beremoved from the part after the part has been built, without damage tothe part. At present, in conventional stereolithographic apparatus, thesame material is used to build the supports, causing them to adherestrongly to the part. As a result, the subsequent removal of thesupports can lead to ripping or tearing of the part.

Consequently, it is an object of the subject invention to provide anapparatus of and method for providing three-dimensional objects throughthe principles of stereolithography, but which employ the use ofnormally solid materials which are made flowable upon the application ofthermal radiation such as heat. It is a further object to provide suchan apparatus which can be coupled to a conventional stereolithographicapparatus. It is a further object to provide a stereolithographicapparatus which enables rapid substitution of materials throughout partbuilding. It is a further object to provide a stereolithographicapparatus for and method of forming three-dimensional objects whichenable the use of a different support material from the material used tobuild the part, which support material is chosen so that it is easilyremovable from the part.

Additional objects and advantages will be set forth in the descriptionwhich follows or will be apparent to those or ordinary skill in the artwho practice the invention.

SUMMARY OF THE INVENTION

To achieve the foregoing objects, and in accordance with the purpose ofthe invention as broadly described herein, there is provided apparatusfor and related methods of forming a three-dimensional object,comprising: a frame; a container of a material which is normally in asolid state, and which is flowable when subjected to synergisticstimulation; first means for applying said synergistic stimulation tothe material in the container whereupon the material in the container iscaused to be flowable; a nozzle coupled to the container for dispensingthe flowable material from the container through an outlet in thenozzle; second means responsive to control signals for controlling theflow of flowable material dispensed by the nozzle; a movable platform;translation means responsive to control signals fixed to the frame fortranslating the nozzle to a predetermined position relative to themovable platform; and at least one control computer for sending controlsignals to the second means, and the translation means, to apply thesynergistic stimulation to the material to obtain flowable material andto selectively dispense the flowable material to form saidthree-dimensional object substantially layer-by-layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of an apparatus of the subjectinvention wherein a part is built from a normally solid material whichis made flowable upon being heated;

FIG. 2 illustrates the use of a second such material to provide supportto otherwise unsupported portion of cross-sections; and

FIG. 3 illustrates a second embodiment of an apparatus of the subjectinvention comprising the apparatus of FIG. 1 coupled to a conventionalstereolithographic apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the apparatus of the subject invention is illustratedin FIG. 1. As illustrated, the apparatus comprises dispensing nozzle 1,x-y translation means 2, flexible tube 3, frame 4, and movable platform5. The dispensing nozzle is coupled to the x-y translation means, which,in turn, is coupled to the frame. The x-y translation means is capableof moving the nozzle to any x, y position within a plane, as shown. Anexample of a translation table is that available from Daedal, Inc.,Harrison City, Pa. The nozzle is advantageously coupled to a source ofmaterial (not shown) by means of flexible tube 3, which providesmaterial from the source to the dispensing nozzle. The platform 5 isadvantageously coupled to a z-stage elevator (not shown), which iscoupled to the frame, and is capable of moving the platform in the z-dimension relative to the frame. The x, y, and z dimensions areindicated in the figure. The z- stage elevator and the x-y translationmeans are advantageously coupled to a control computer, which, in turn,is advantageously coupled to a CAD system or the like. The translationmeans is capable of moving the nozzle to any x, y position within aplane in response to control signals, and the z- stage elevator, also inresponse to control signals, is capable of moving the platform to anyposition in the z-dimension along a path substantially perpendicular tothe plane. Together, the translation means and the z- stage elevatorprovide a capability to selectively dispense material to any selectedposition on the platform, as well as to positions on a partially-formedpart above the platform in the course of building up the part.

The dispensing nozzle is advantageously fitted with removable tip lahaving an outlet of a particular size. The size of the outlet can bedetermined based on the particular application, and a tip with theappropriate size outlet can then be fitted to the nozzle. The size ofthe outlet determines the resolution of the final part. For parts wherehigh resolution is not required, a tip with a relatively large outletcan be used, while for other parts, where high resolution is important,a tip with a small outlet can be used. Alternatively, different tips canbe used throughout the building of a single part. For example, a tipwith a small outlet could be used to form the boundaries of a part,where high resolution might be required, while a tip with a largeroutlet could be used to rapidly fill in the areas within the boundaries.

As shown, the nozzle is advantageously coupled to a source of materialby means of flexible tube 3. Preferably, the material is a materialwhich is normally solid at room temperature, but which is renderedflowable when heated above its melting point. Possible materials includethermoplastics, hot-melt glue, wax, and cerro alloys (which typicallyhave melting temperatures ranging from 150 to 340 degrees Fahrenheit).After it is dispensed, the material should be viscous enough to stay inplace until it solidifies. In addition, it must be thin enough to bedispensed through the outlet.

The material is advantageously heated above its melting temperature atthe source to render it flowable by means of a heater or the like (notshown). The material, once melted, will flow from the source to thenozzle by means of flexible tube 3. Alternatively, the source (and theheater) could be integrated with the nozzle, and the tube could then beeliminated. In this instance, both the integrated source and nozzlewould be coupled to and movable by the x-y translation means.

When the material is relatively viscous, or the outlet of the nozzlerelatively small, the material can be dispensed through the nozzle uponthe application of pressure from a source (not shown). Air pressure ispreferable, but an alternative form includes mechanical pressure asdeveloped with a piston-type plunger. When the material is less viscous,or the outlet of the nozzle is larger, the material can be dispensedthrough the force of gravity.

The flow of material can be stopped by means of slidable valve 1b, inresponse to control signals, to physically block the flow.Alternatively, in those instances where flow has been initiated bypressure, the flow can be stopped by lessening, ceasing, or reversingthe pressure. During part-building, it may be advantageous toperiodically block the flow of material after a cross-section has beenformed to give the material making up that cross-section time tosolidify. Then, the flow could be allowed to continue, and the materialdisposed to form the next cross-section.

In operation, the apparatus can be used to build a part as follows.First, a representation of the part is optionally provided to thecontrol computer from a CAD system or the like. The control computerthen slices the object representation into a plurality of layerrepresentations collectively known as a building representation. Thecontrol computer then simultaneously directs the x-y movement of thenozzle and the z-movement of the platform in accordance with thebuilding representation to selectively dispense material at theappropriate areas to form the part. First, material will be directlydispensed onto the platform. Then, as part building continues, thematerial from a cross-section will be dispensed onto a previouscross-section.

In practice, as described in U.S. Pat. No. 5,184,307 the controlcomputer can comprise several computers, including a SLICE computer forslicing the object representation into a building representation, and aPROCESS computer for sending control signals to and directing movementof the x-y translation means and z-stage elevator, and for controllingthe flow of material through the nozzle.

In FIG. 1, cross-section 6b is formed by moving the platform until theprevious cross-section is situated an appropriate vertical distancebelow the nozzle. Then, in accordance with the building representation,an appropriate volume of material is dispensed from the nozzle inaccordance with the layer thickness prescribed by the buildingrepresentation, while the nozzle is moved to the appropriate x, ylocations on the working surface (which may either be the platform or aprevious cross-section) in accordance with the prescribed pattern forthe cross-section specified by the building representation.

After the material for the cross-section has been dispensed, it willthen cool and harden into the next cross-section, and simultaneouslyadhere to the working surface, advantageously through the naturaladhesive properties of the material as it cools. Alternatively, apressure or heat-sensitive adhesive could be applied to ensure evengreater adhesion.

The flow of material is then blocked, the platform lowered, and the nextcross-section 6a formed in the manner previously described. In thismanner, the final part 6 is formed, cross-section by cross-section,according to the general principles of stereolithography.

After the part has been formed, it can be removed from platform 5 byheating the platform, thereby melting the thin layer of material bondingthe part to the platform. Alternatively, this bond can be broken bysawing or cutting.

An advantageous aspect of this embodiment is the ability to rapidlychange materials which are dispensed through the nozzle. This can simplybe accomplished by substituting one source of material for another bysimply connecting the remote end of flexible tube 3 to a differentsource. Alternatively, many different sources can be coupled to thenozzle through their own respective tubes, the control of the flow ofmaterial from each source to the nozzle being controlled by a slidablevalve or other means, for each tube, as previously described.

After a cross-section has been formed out of a first material, forexample, it may be advantageous to fill the hollow areas on thatcross-section with a second material in order to provide support forportions of the next cross-section. The second material can be chosensuch that it can easily be removed from the final part after building iscomplete. One way to accomplish this is to employ a second materialwhich has a lower melting point than the material used to built thepart.

In FIG. 2, for example, part 7 is illustrated. The object representationused to construct the part is identified with reference numeral 8, andthe cross-sections of the built part are denoted by numerals 7a, 7b,etc. As indicated, in this example, the part is built in an oversizedstyle relative to the object representation.

As shown, each of the part layers will have some unsupported portions.The portions of cross-section 7a which are unsupported will be portions9a and 9b.

These unsupported portions may be problematic, especially since thematerial may not harden immediately upon leaving nozzle 1, but insteadmay, for a time, remain flowable after it has been deposited. In thisinstance, especially if the unsupported sections are in the shape of acantilevered beam or the like, the unsupported portions may collapseunless means are provided to support the unsupported portions, at leastuntil the material making up these portions has solidified enough sothat these portions will support themselves.

An advantageous way to provide support is by dispensing a second supportmaterial in the appropriate regions on the previous cross-section inorder to support the unsupported portions of the next cross-section. InFIG. 2, for example, cross-hatched areas 11a and 11b might be filledwith a support material in order to support portions 9a and 9b.

This support material, like the building material used to build thepart, can have the properties of being normally solid, of being flowableupon being heated, and then solidifying after it is being dispensed fromthe nozzle. However, the support material should have the property ofbeing easily separable from the part at a later stage of processing. Asmentioned previously, one way to accomplish this by utilizing a supportmaterial which has a lower melting point than the building material.

The support material is preferably wax, a thermoplastic, hot melt glue(such as that dispensed from a hot melt glue gun), a metal having alower melting point than the first material, a powder, or a liquid ofhigher density than the first material and which does not bond to it.Possible liquids include heavy water, a fluorocarbon, heavyfreoncachloroflyorcarbon, ethylene glycol, or salt water.Advantageously, the support material should be a good thermal conductor.This property will speed up the time it takes for the building materialto solidify after it has been dispensed, since it will facilitate theconduction of heat away from this material.

To provide support to the next cross-section, the hollow areas in aparticular cross-section which are not to be solidified into the finalpart (hereinafter referenced to as the "void" or "hollow" areas) can befilled with the support material. As discussed previously, this can beaccomplished simply by changing the source of the material coupled tothe nozzle.

Also, as discussed previously, the building material is normally a solidat room temperature. Alternatively, if the part 6, while it is beingformed, is kept below room temperature, a building material can be usedwhich is a liquid at room temperature, as long as the part is kept belowthe freezing point of the material, so that the building material willsolidify upon contacting the partially-formed part.

The speed with which this material, after it has been dispensed, willsolidify, depends on the thermal conductivity of the immediateenvironment surrounding the material after it has been dispensed. Thisenvironment will typically include the previous cross-section, anysupport material from the previous cross-section, and the air. As aresult, it will be advantageous to keep the already-formedcross-sections and support material substantially below the meltingpoint of the building material in order to speed up the solidificationprocess.

In the case where a thermally-flowable support material is used whichsolidifies after it is dispensed, it is advantageous to utilize asupport material having a lower melting point than the buildingmaterial. This property will enable the support material, after it hassolidified, to simply be melted off of the part without damaging it.This separation can be accomplished after the next cross-section hasbeen solidified, since this cross-section would then no longer needsupport. Alternatively, separation can be effectuated after the entirepart has been built.

The support material, after it has been dispensed, should be maintainedbelow its melting point, even after it is placed in contact withjust-dispensed building material, which will typically still be hot.Otherwise, the support material will melt when it is placed in contractwith the just-dispensed building material.

To accomplish this, a support material should be used which has a highenough thermal conductivity so that it does not melt when placed incontact with the building material. Alternatively, if the temperature ofthe support material is kept low enough, it may not have to be a goodthermal conductor providing it has a high enough heat capacity at theinterface with the building material so that it does not melt.

In some cases, it may be desirable to use a support material having ahigher melting temperature than the building material since this willfacilitate the creation of hollow molds or the like, which cansubsequently be used to produce the part on a production scale.

In FIG. 2, for example, the hollow areas in all the cross-sections canbe filled in with such a support material. Then, after the part has beenformed, the building material could be melted and drained off withoutdamaging the solidified support material.

Additional elements could be added to cool the building material as itexits the nozzle. For example, a hose (not shown) can be situated nearthe nozzle outlet to divert a spray of air or water mist towards thematerial as it is being dispensed. Alternatively, a gas or a liquidhaving a lower density than the building material, and hence capable ofabsorbing heat from the building material, can be directed towards thenozzle.

Alternative means of providing support other than the use of supportmaterial to fill hollow areas in object cross-sections can be utilized.One alternative approach comprises altering the order in which thebuilding material on a cross-section is dispensed. Instead of simplydispensing the material from one side of the cross-section to the other,this approach comprises first dispensing the material to those portionsof the cross-section which are supported, and then radially extendingthose cross-sections to include the unsupported portions. In FIG. 2, forexample, for the building of cross-section 7b, building material mightinitially be dispensed at portion 9c, and then be extended radially toinclude portions 9a and 9b. Provided that the unsupported portions 9aand 9b are not too large, support will be provided to them by thesupported portion 9c.

A third approach to providing support is the use of a support materialto actually build supports, such as web supports, as described in U.S.Pat. No. 4,999,143. Such a support material would have all theproperties discussed previously, e.g., it would preferably have a lowermelting point than the building material so that it could later beseparated from the part without damaging the part. FIG. 2 illustratesweb support 10 which spaces the part 7 from the platform 5, and whichalso supports the part from the bottom surface. As discussed in U.S.Pat. No. 4,999,143, web supports could also be used to support portionsof a part other than the bottom surface, such as a cantilevered surface.These surfaces could be supported by a web support connecting thesurface to the platform, or alternatively, to another part surface. Theweb support in FIG. 2 is comprised of three cross-sections, numbered10a, 10b, and 10c, each of which could be formed using the supportmaterial in the manner described previously.

It is advantageous to be able to incorporate the teachings of thesubject invention into a conventional stereolithography apparatus, i.e.,one employing a container of a material capable of physicaltransformation upon selective exposure to synergistic stimulation suchas a polymerizable resin which solidifies upon a UV laser beam, arecoating means such as a z-stage elevator, and means such as a doctorblade or the like to rapidly coat fresh layers of resin over previouscross-sections.

An apparatus which incorporates these teachings is illustrated in FIG.3, in which, compared to FIG. 1, like elements are referred to with likereference numerals. The additional elements in FIG. 3 not previouslydiscussed are container 13 containing a material capable of physicaltransformation upon selective exposure to synergistic stimulation, suchas a polymerizable resin which solidifies upon a exposure to UVradiation, a doctor blade (not shown), a source synergistic stimulationsuch as a UV laser (not shown) which emits a UV laser beam, androtatable scanning mirrors (not shown) capable of directing the UV laserbeam to a point on the material surface 14. Part 6 is shown as beingformed, and spaced from platform 5, by already-formed web supports 12aand 12b. The platform, as before, is coupled to a z-stage elevator (notshown), which is capable of raising the platform into and out of thecontainer of material, below the material surface if necessary, and alsoto a position proximate to nozzle 1.

Each cross-section of the supports 12a and 12b, and the part 6, can beformed from a material dispensed through the nozzle, or from materialcontained in the container. Material from the nozzle will be selectivelydispensed in the manner previously described. Fresh material from thecontainer will not be selectively dispensed, but instead will berecoated over the platform or previous cross-section in the conventionalmanner, i.e., by overdipping the platform or previous cross-sectionbelow the material surface, whereupon a fresh layer of material flowsover the platform or previous cross-section, and then up-dipping theupper surface of the fresh layer of material above the material surface,whereupon excess resin is swept away by the doctor blade. Afterrecoating, the fresh layer of material is then typically selectivelyexposed to the synergistic stimulation.

Many building methods are possible with this apparatus. For example, websupports could be formed out of normally solid, thermally-flowablematerial dispensed from the nozzle, and the part could be formed out ofa material capable of selective physical transformation upon exposure tosynergistic stimulation, which is contained in a container. Moreover,the hollow areas of the cross-sections could be filled in with thenormally-solid, thermally-flowable material dispensed from the nozzle toprovide even additional support.

In this instance, part formation would proceed as follows. First,support material in the nozzle would be selectively dispensed onto theplatform or previous cross-section in those areas which will not be partof the final part, and then allowed to solidify. In FIG. 2, for example,this material would be dispensed in areas 11a and 11b of cross-section7b. This material would not be dispensed into the areas on thecross-section which are to solidify into the final part. After thissupport material has solidified, a mold in the shape of the partcross-section will be formed. Then, the platform and the upper surfaceof this solidified support material could be down-dipped deeply belowmaterial surface 14, causing fresh building material from the containerto flow into those areas on the cross-section which are to be solidifiedinto the final part. In FIG. 2, for example, deep down-dipping willcause area 9c to fill with the building material from the container. Theplatform could then be up-dipped and the doctor blade or the likeutilized to sweep away any excess material. Next, this building materialwould be selectively exposed to the synergistic stimulation in theconventional manner, i.e., by rotating the mirrors to trace the beamalong the surface of this material in a prescribed pattern.Alternatively, this material could be flood-exposed to the synergisticstimulation. Flood exposure rather than selective exposure is possiblesince any excess material has already been removed which couldconceivably be improperly solidified. This has been accomplished by theaction of the doctor blade, but also by the previous step of dispensingthe normally solid, thermally-flowable support material to effectivelyform a mold of the part cross-section. This latter step ensures thatlittle or no excess material from the container will be present in theseareas which could be improperly solidified.

This process could continue for the formation of the next cross-section.The support material could then be removed in the manner previouslydescribed.

Note that by dispensing the support material before recoating with thebuilding material ensures that excess support material will not solidifyover those portions of the solidified building material which will beadhered to adjacent part cross-sections. As a result, a machining stepwhereby any such excess support material would need to be machined offin order to ensure adherence is eliminated.

Alternatively, it may be advantageous to add a machining step beforerecoating with the building material in order to smooth the solidifiedsupport material. This might facilitate the flow of building materialover the solidified support material, and may even facilitate sweepingwith the doctor blade or the like, during the recoating step. To avoidany damage to the solidified material during the recoating step, it maybe advantageous to perform sweeping with a squeegee rather than a doctorblade.

In the above description, the support material is the normally-solidthermally-flowable material selectively dispensed from the nozzle, andthe building material is the material in the container capable ofselective physical transformation upon exposure to the synergisticstimulation. Alternatively, one of ordinary skill may appreciate thatthe support structure, whether web supports or layer-by-layer support,could be formed out of the material in the container, and the part couldbe formed out of the material dispensed from the nozzle.

While embodiments and applications of this invention have been shown anddescribed, it should be apparent to those skilled in the art that manymore modifications are possible without departing from the inventiveconcepts herein. Specifically, the invention is intended to encompassstereolithographic part building employing any material which isnormally in a solid state and which is flowable when subjected to anyform of synergistic stimulation. Included are materials made flowableupon conduction of heat, through application of a probe or the like, orthrough ion or particle bombardment or the like. Also included arematerials made flowable upon application of radiation of heat from a CO₂or infrared laser, or the like. The invention is further intended toencompass materials which are made flowable upon the application of heatthrough a chemical reaction, such as where heat is released when a firstmaterial is placed in contact with a second material, causing the firstmaterial to be made flowable, or where the first and second materialsare placed in contact with a third material, causing the third materialto be made flowable. The invention, therefore, is not to be restricted,except in the spirit of the appended claims.

What is claimed is:
 1. An apparatus for forming a three-dimensionalobject comprising:a frame; at least one container for containing abuilding material which is normally in a solid state and which is madeflowable when maintained at or above a flowable temperature; means formaintaining said building material at a temperature at or above saidflowable temperature thereby forming flowable building material; abuilding environment maintained at a temperature below said flowabletemperature and including a platform on which to support at least aportion of the three-dimensional object; at least one dispenser coupledto the at least one container for dispensing said flowable buildingmaterial from said container and into said building environment; meansfor actively cooling the building material as it enters said buildingenvironment; at least one computer programmed to identify locationswhich comprise the object and to transmit said locations as positioningcontrol signals; means for using said positioning control signals toposition the at least one dispenser relative to said platform; and meansto selectively dispense flowable building material to at least someobject locations.
 2. The apparatus of claim 1 wherein the means forcooling the building material further comprises means for dispensing afluid capable of absorbing heat from the building material, into saidbuilding environment.
 3. The apparatus of claim 1 wherein the means forcooling the building material comprises means for directing a fluidtoward said building material as said building material is dispensedfrom said dispenser.
 4. The apparatus of claim 2 wherein the means forcooling the building material further comprises means for dispensing aliquid having a lower density than said building material.
 5. Theapparatus of claim 2 wherein the means for cooling the building materialfurther comprises means for dispensing a gas.
 6. The apparatus of claim1 further comprising means for selectively dispensing said buildingmaterial on a cross-section-by-cross-section basis.
 7. An apparatus forforming a three-dimensional object comprising:a frame; at least onecontainer for containing a building material which is normally in asolid state and which is made flowable when maintained at or above aflowable temperature; means for maintaining said building material at atemperature at or above said flowable temperature thereby formingflowable building material; a building environment maintained at atemperature below said flowable temperature and including a platform onwhich to support at least a portion of the three-dimensional object; atleast one dispenser coupled to the at least one container for dispensingsaid flowable building material from said container into said buildingenvironment; means to apply an adhesive to ensure adhesion between saiddispensed material and a working surface; at least one computerprogrammed to identify locations which comprise the object and totransmit said locations as positioning control signals; means for usingsaid positioning control signals to position the at least one dispenserrelative to said platform; and means to selectively dispense saidflowable building material to at least some object locations.
 8. Amethod of forming a three-dimensional object comprising thesteps:containing a building material which is normally in a solid stateand which is made flowable when maintained at or above a flowabletemperature; maintaining said building material at a temperature at orabove said flowable temperatures thereby forming flowable buildingmaterial; maintaining a building environment at a temperature below saidflowable temperature; supporting at least a portion of the object on aplatform situated within said building environment; identifyinglocations which comprise the object; transmitting positioning controlsignals for said identified locations; positioning at least onedispenser relative to said platform to allow selective dispensing offlowable building material to at least some object locations; dispensingsaid flowable building material from said container into said buildingenvironment; and actively cooling said building material as it enterssaid building environment.
 9. The method of claim 8 wherein the step ofactively cooling the building material comprises dispensing a fluid intosaid building environment, said fluid capable of absorbing heat from thebuilding material.
 10. The method of claim 9 wherein the step ofactively cooling the building material further comprises directing saidfluid toward said building material as it is dispensed from saiddispenser.
 11. The method of claim 9 wherein the step of activelycooling the building material comprises dispensing a liquid having alower density than said building material.
 12. The method of claim 9wherein the step of actively cooling the building material comprisesdispensing a gas.
 13. The method of claim 8 additionally comprising thestep of dispensing said building material on across-section-by-cross-section basis.
 14. A method of forming athree-dimensional object comprising the steps:containing a buildingmaterial which is normally in a solid state and which is made flowablewhen maintained at or above a flowable temperature; maintaining saidbuilding material at a temperature at or above said flowabletemperatures thereby forming flowable building material; maintaining abuilding environment at a temperature below said flowable temperature;supporting at least a portion of the object on a platform situatedwithin said building environment; identifying locations which comprisethe object; transmitting positioning control signals for said identifiedlocations; positioning at least one dispenser relative to said platformto allow selective dispensing of flowable building material to at leastsome object locations; dispensing said flowable building material fromsaid container into said building environment; and applying an adhesivebetween at least some of the dispensed building material and a workingsurface.
 15. An apparatus for forming a three-dimensional object,including formation of a removable support structure, comprising:aframe; at least one container for separately containing a buildingmaterial and a support material wherein at least the building materialis normally in a solid state and which is made flowable when maintainedat or above a flowable temperature; means for maintaining at least thebuilding material at a temperature at or above said flowable temperaturethereby forming flowable material; a building environment maintained ata temperature below said flowable temperature and including a platformon which to support at least a portion of at least one of said buildingmaterial and said support material; at least one dispenser, coupled tothe at least one container, for selectively dispensing said buildingmaterial and said support material into said building environment; meansfor positioning said at least one dispenser relative to said platform;means for actively cooling said building material upon being dispensedinto said building environment; and at least one computer programmed totransmit positioning control signals for controlling said means forpositioning, and for controlling said dispensing.
 16. The apparatus ofclaim 15 wherein the means for cooling the building material comprisesmeans for dispensing a fluid into said building environment, said fluidcapable of absorbing heat from the building material.
 17. The apparatusof claim 16 wherein the means for cooling further comprises means fordirecting said fluid towards the building material as it is dispensedfrom said dispenser.
 18. The apparatus of claim 16 wherein the means forcooling comprises means for dispensing a liquid having a lower densitythan said building material.
 19. The apparatus of claim 16 wherein themeans of cooling comprises means for dispensing a gas.
 20. An apparatusfor forming a three-dimensional object, including formation of aremovable support structure, comprising:a frame; at least one containerfor separately containing a building material and a support materialwherein at least a selected one of said building material and saidsupport material is normally in a solid state and which is made flowablewhen maintained at or above a flowable temperature; means formaintaining said selected one at a temperature at or above said flowabletemperature thereby forming flowable material; a building environmentmaintained at a temperature below said flowable temperature andincluding a platform on which to support at least a portion of at leastone of said building material and said support material; at least onedispenser, coupled to the at least one container, for selectivelydispensing said building material and said support material into saidbuilding environment; means for positioning said at least one dispenserrelative to said platform; means for applying an adhesive to at least aportion of dispensed material to ensure adhesion between the dispensedmaterial and a working surface; and at least one computer programmed totransmit positioning control signals for controlling said means forpositioning, and for controlling said dispensing.
 21. A method offorming a three-dimensional object, including formation of a removablesupport structure, comprising the steps:separately containing a buildingmaterial and a support material, wherein said building material isnormally in a solid state and which is made flowable when maintained ator above a flowable temperature; maintaining said building material at atemperature at or above said flowable temperature thereby formingflowable material; maintaining a building environment at a temperaturebelow said flowable temperature; supporting at least a portion of atleast one of said building material and said support material on aplatform within said building environment; identifying as positioningcontrol signals locations which comprise the object and locations whichare exclusive of the object; transmitting positioning control signalsfor said identified locations; positioning at least one dispenserrelative to said platform, using said transmitted positioning controlsignals; selectively dispensing said building material from the at leastone dispenser coupled to the at least one container, into said buildingenvironment and to at least some object locations; selectivelydispensing said support material from the at least one dispenser coupledto the at least one container, to at least some of the regions adjacentto said regions of said dispensed building material; and activelycooling said building material upon dispensing into said buildingenvironment.
 22. The method of claim 21 wherein the step of activelycooling comprises dispensing a fluid into said building environment,said fluid capable of absorbing heat from the building material.
 23. Themethod of claim 22 wherein the step of actively cooling furthercomprises directing said fluid towards the building material whendispensing from said dispenser.
 24. The method of claim 22 wherein thestep of cooling comprises dispensing a liquid having a lower densitythan the building material.
 25. The method of claim 22 wherein the stepof cooling comprises dispensing a gas.
 26. The apparatus of claim 7wherein the means to apply an adhesive comprises means to apply apressure sensitive adhesive.
 27. The apparatus of claim 7 wherein themeans to apply an adhesive comprises means to apply a heat-sensitiveadhesive.